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Category: Bacterial Pathogenesis
Function and Expression of Legionella pneumophila Surface Factors, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817985/9781555812300_Chap08-1.gif /docserver/preview/fulltext/10.1128/9781555817985/9781555812300_Chap08-2.gifAbstract:
This chapter focuses on the major infectivity potentiator protein (Mip) protein and the function and expression of the flagellum of Legionella pneumophila. The Mip protein forms a homodimer on the bacterial surface; each monomer consists of a proximal and a peripheral domain. The contact regions between the two monomers seem to be located at the N-terminal part of the protein. Motility is an important factor to find a new host for another cycle of intracellular replication and for colonization of new habitats. Flagellated bacteria have been found in lung alveolar spaces of patients with legionellosis. It was shown that expression of the virulent phenotype and motility is regulated coordinately. A gentamicin infection assay revealed a clear difference in the number of intracellular bacteria at the onset of multiplication. L. pneumophila is found in very different habitats and it is able to replicate intracellularly in many host cells. Researchers recently demonstrated that regulation of fiaA expression is modulated by different environmental factors, such as temperature, growth phase, osmolarity, viscosity, and the nutrient stage.
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Electron micrographs showing the flagellated wild-type strain L. pneumophila Corby (A) and the nonflagellated mutant strain KH3 (B). Bacteria were grown to stationary phase at 30°C, suspended in water, and applied to Formvar coated copper grids. Samples were shadowed with platinum-palladium and examined with a Zeiss 10A transmission electron microscope. Bars, 0.5 μm.
Electron micrographs showing the flagellated wild-type strain L. pneumophila Corby (A) and the nonflagellated mutant strain KH3 (B). Bacteria were grown to stationary phase at 30°C, suspended in water, and applied to Formvar coated copper grids. Samples were shadowed with platinum-palladium and examined with a Zeiss 10A transmission electron microscope. Bars, 0.5 μm.
Gentamicin assay of L. pneumophila Corby wild-type, the flaA mutant strain (KH3), and the complemented mutant strain (CD 10) with A. castellanii (A) and HL-60 cells (B). Host cells were incubated with legionellae at a multiplicity of infection of 10 for 2 h. Extracellular bacteria were killed by incubation with gentamicin (80 μg/ml) for 1 h, and the CFUs were determined by plating on ABCYE agar plates (t = 0). The rate of intracellular multiplication (t = 0 to t = 24) is given above or beneath the error bars. Error bars indicate the standard deviation obtained from three independent experiments.
Gentamicin assay of L. pneumophila Corby wild-type, the flaA mutant strain (KH3), and the complemented mutant strain (CD 10) with A. castellanii (A) and HL-60 cells (B). Host cells were incubated with legionellae at a multiplicity of infection of 10 for 2 h. Extracellular bacteria were killed by incubation with gentamicin (80 μg/ml) for 1 h, and the CFUs were determined by plating on ABCYE agar plates (t = 0). The rate of intracellular multiplication (t = 0 to t = 24) is given above or beneath the error bars. Error bars indicate the standard deviation obtained from three independent experiments.
Effects of different environmental factors on the flagellin expression of L. pneumophila Corby (pKH23, pflaA-luxAB fusion). L. pneumophila was grown in YEB medium at 37°C supplemented with 1% glucose, 30 mM serine, 200 mM sucrose (osmolarity), or 6% polyvinylpyrrolidone (PVP) (viscosity). Cells were harvested at the late exponential growth phase and luciferase activity was measured and is given in relative light units (RLU). Error bars indicate the standard deviation obtained from three independent experiments. □, control;
, 1% glucose;
, 30 mM serine;
, 200 mM sucrose;
, 6% PVP.
Effects of different environmental factors on the flagellin expression of L. pneumophila Corby (pKH23, pflaA-luxAB fusion). L. pneumophila was grown in YEB medium at 37°C supplemented with 1% glucose, 30 mM serine, 200 mM sucrose (osmolarity), or 6% polyvinylpyrrolidone (PVP) (viscosity). Cells were harvested at the late exponential growth phase and luciferase activity was measured and is given in relative light units (RLU). Error bars indicate the standard deviation obtained from three independent experiments. □, control;
, 1% glucose;
, 30 mM serine;
, 200 mM sucrose;
, 6% PVP.